1. Field of the Invention
The present invention relates generally to a system for controlling positions of record tracks relative to a scanning trace of a head device, and more particularly, to a control system for adjusting travelling speed of a record tape to control positions of record tracks formed on the record tape relative to a scanning trace of a reproducing head device which is driven to scan the record tape along a scanning path transverse to the record tracks on the record tape.
2. Description of the Prior Art
There has been proposed a so-called digital audio tape recorder (referred to as DAT, hereinafter) which is operative in a recording operation mode to convert an audio signal into digital data and to record the digital data based on the audio signal onto a magnetic record tape with increased recording density. The recorder is further operative in a reproducing operation mode to read digital data, based on audio from a magnetic record tape on which the digital data are recorded with increased recording density, and to convert the digital data read from the magnetic record tape into the audio signal. In the DAT, a pair of rotary magnetic heads are mounted on a rotary head cylinder to be disposed at angular intervals of, for example 180 degrees therebetween, for scanning alternatively the magnetic record tape which is wound on the rotary head cylinder. In the recording operation mode, the digital data obtained based on the audio signal are supplied to the rotary magnetic heads to be recorded in record tracks formed on the magnetic record tape successively by each of the rotary magnetic heads; and in the reproducing operation mode, the digital data of the audio signal read from the record tracks on the magnetic record tape are derived alternatively from each of the rotary magnetic heads.
In the reproducing operation mode of the DAT, it is usual that a normal reproduction is performed with the rotary magnetic heads which scan alternately the magnetic record tape to trace each of the record tracks thereon so that the digital data recorded in each record track are fully and continuously reproduced. With such a system a fast-forward reproduction occurs in which the rotary magnetic heads scan alternately the magnetic record tape along a scanning path transverse to a plurality of record tracks on the magnetic tape. Thus, the digital data recorded in each of the record tracks traversed by the rotary magnetic head are partially and intermittently reproduced. This is desired to be performed in addition to the normal reproduction.
In view of this, it has been also proposed in the field of the DAT to cause the magnetic record tape on which the digital data of the audio signal are recorded in the record tracks to travel at a speed higher than that in normal reproduction so that a plurality of record tracks on the magnetic record tape are traversed by the rotary magnetic head on each scanning of the magnetic record tape; and the digital data recorded in each of the record tracks traversed by the magnetic record head are partially and intermittently reproduced.
However, in the case of fast-forward reproduction thus proposed previously, the positions of the record tracks traversed by the rotary magnetic head relative to a scanning trace of the rotary magnetic head on the magnetic record tape are uncertain; and the level of the digital data of the audio signal read partially from each of the record tracks traversed by the rotary magnetic head at each scanning of the magnetic record tape is directly influenced by variations in the positions of the record tracks relative to the scanning trace of the rotary magnetic head. This results in a disadvantage that a reproduced audio signal obtained in fast-forward reproduction by the DAT is not stabilized in level, and thus sound obtained based on the reproduced audio signal becomes harsh to the ear.